The present invention is useful in the field of image processing. Substantial information regarding a scene can be obtained by utilizing the spectral content of the scene. Spectral image processing is advantageous in satellite land use surveys and in target identification in a cluttered scene.
In the field of land use analysis, it is known to employ spectral analysis of reflected ambient radiation received by a moving platform. It is typical to use a technique called "push broom" in which an aircraft or satellite employs a sensor for viewing a number of cross track pixels and the motion of the platform scans this viewed region along the track of motion. It is known in the art to employ linear combinations of spectral bands of the received data to form dimension reduced characteristics. The characteristics of any particular pixel can be plotted on a graph of such characteristics permitting land use classification by its spectral character as taught by E.P. Christ and R.C. Cicone, "A Physically Based Transformation of Thematic Mapper Data - The TM Tasseled Cap," IEEE Trans. on Geoscience and Remote Sensing, Vol. GE-22, No. 3, pp. 256-263 (1984).
In addition, analysis of the spectral character of a pixel can aid in target classification. It is known that certain target types have spectral characteristics which permit identification and classification. A further use of spectral analysis includes enhancement of target spectral characteristics while simultaneously suppressing known background clutter characteristics. This technique has the potential for greatly improving the capability of target detection.
In order to perform such spectral analysis, it is necessary to produce a spectrally weighted value or values from the electromagnetic radiation received from the area of interest. This process can be performed by detection of the radiation intensity using an electronic detector, followed by electronic analysis of this signal. The processing can be carried out using a digital computer. In general, however, the amount of processing required for the solution of many practical problems in real time is beyond the capability of any present or proposed future computer system. Thus either the benefit of this technique is lost or the processing must take place after the scene detection at the slower rate of the processing system.
Therefore there is a need in the art for a manner of producing one or more spectrally weighted values from the radiation received from a pixel of interest in real time at the rate of pixel imaging.